Future industry needs may include application specific integrated circuits whose manufacture will require flexible fabrication and processing equipment. The flexibility of this equipment will enable meeting the specifications of differing integrated circuit designs. Substantial improvements in sensor and process control development will be important to the realization of such flexible semiconductor manufacturing systems. The characterization of functional relationships involved in the deposition, photo-resist, patterning, and etching processes used to fabricate integrated circuit devices is an essential part of developing flexible and cost-effective manufacturing processes for advanced integrated circuit devices. For example, the plasma chemistry of etching systems involves complex nonlinear behavior with numerous chemical reactions interacting with electrical and physical affects. Accurate characterization and monitoring of this behavior is important. However, as a result of the complexity, characterization and monitoring of the process operating space can be extremely difficult.
Equipment sensors such as RFM, OES, and other added sensors, as well as built-in sensors, are a double edged sword. Sensors provide information used to characterize functional relationships, but the quantity of information can be prohibitive. Processing multiple real time sensor information is complex, and beyond the capability of conventional systems.
Conventional process control strategies often are developed only through expensive and time consuming trial and error methods and are unlikely to provide either the flexibility or cost efficiency necessary to implement a competitive production process for future integrated circuit devices. In these conventional systems, relationships between process and control parameters are developed through trial and error to generate process recipes. These recipes can be inflexible and not adaptive to conditions within the processing equipment as the conditions change with repeated use. For example, in a plasma etch reactor, a conventional recipe may not compensate for thin film buildup on reactor walls.
Conventional approaches to processing equipment fault detection and classification have relied solely on directly measurable sensor feedback. Obvious faults such as an equipment sensor failure are detectable, and periodic recalibrations are necessary to bring drifting sensors back to defined norms. However, conventional monitoring and fault detection systems and methods do not address adequately the problem of sensor failure detection, sensor bias, and sensor drift meet current and future industry needs.
Specifically with respect to plasma etch systems, conventional processing equipment monitors the process state (plasma condition) in the form of end-point detection using mono-chromatic spectral line detectors to determine when the etch process has completed. A number of conventional systems also use multi-chromatic spectral analysis of plasma in order to determine some of the physical phenomena of plasma etching including detection and measurement of interacting chemical species within the plasma during various stages of etch.